Fever of unknown origin (FUO) is a challenging diagnostic condition. The differential diagnosis of FUO includes a broad spectrum of highly diverse diseases which are mainly subdivided into four groups: infectious, non-infectious inflammatory process, malignancies and undiagnosed cases. [1-4]. Nuclear medicine modalities are capable of early detection of disease activity at a cellular and molecular level and to distinguish between active and inactive disease [5]. 18-Fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) is an important imaging modality for the investigation of FUO [6].
